An optical fiber-based sensor system may comprise an optical fiber with fiber Bragg gratings. Patent publication WO 02/10677 discloses an optical sensing device containing fiber Bragg gratings, a scanning band pass filter an interferometer and multiple photo detectors. A scanning Fabry-Perot band pass filter is used to wavelength-multiplex multiple gratings in a single fiber. An unbalanced Mach-Zehnder fiber interferometer made with a 3×3 coupler can detect strain-induced wavelength shifts.